JPS6374006A - Polarizing plate - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display body which has no possibility of a decrease in the transparency and has excellent display performance by unitizing a polarizable film and transparent plastic plate by a satd. copolymer polyester film, thereby forming a polarizing plate. CONSTITUTION:The upper polarizing plate 1 below the transparent plastic plate 3 consists of the satd. copolymer polyester film 11 provided on one face of the polarizable film 10 and a pressure-sensitive adhesive layer 12 provided on the other face of the polarizable film 10. A liquid crystal cell 2 is constituted of glass 20 for the liquid crystal cell and a liquid crystal 21 housed in the glass 20. The pressure-sensitive adhesive layer 12 is adhered to the glass 20 for the liquid crystal cell and the satd. copolymer polyester film 11 is adhered to the transparent plastic plate 3. Since a reflection layer 4 provided to the lower polarizing plate 1' is generally extremely thin, said layer is adhered to the polarizable film 10' by the pressure-sensitive adhesive layer 12' in place of the polyester film 11 of the upper polarizing plate 1 and further, the polarizable film 10' is adhered by the pressure-sensitive adhesive layer 12' to the liquid crystal cell 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polarizing plate suitably used in liquid crystal displays, and particularly to a polarizing plate capable of providing a liquid crystal display with excellent display performance.

(Prior art) A polarizing film is formed by laminating both sides of a polyvinyl alcohol film, which has been given polarizing properties with iodine, dichroic dye, etc., with a protective film such as a cellulose triacetate film. There is. Generally, a liquid crystal display is provided with a pressure-sensitive adhesive layer on the polarizing film,
It is manufactured by pressing dirt onto a liquid crystal cell.

In recent years, as liquid crystal displays have become larger, protective glass with anti-reflection treatment (AR glass) and transparent plastic plates (for example, acrylic plates) are being used to protect polarizing films and improve visibility during use. A protective plate such as a polycarbonate plate is provided on the polarizing film. However, there is a gap between the protective plate and the polarizing film, so that the liquid crystal display is easily damaged. Moreover, these voids are the cause of making the layer J of the liquid crystal display thick.

For this reason, attempts have been made to eliminate voids and make the liquid crystal display thinner while providing a resin film between the polarizing film and the protective plate. Thereby, the liquid crystal display can be layered, and damage to the liquid crystal display caused by voids can be avoided. As the resin film, adhesive thermoplastic resin films such as plasticized polyvinyl butyral have been proposed. This improves the strength of the liquid crystal display.

However, when a transparent plastic plate is used as a protective plate in order to reduce the weight of a liquid crystal display, the transparent plastic plate deteriorates due to bleeding of the plasticizer contained in the polyvinyl butyral film.

The surface has turned white due to the deterioration of the transparent plastic plate.

Transparency decreases, and the display performance of the liquid crystal display is impaired.

(Problems to be Solved by the Invention) The present invention solves the above conventional problems, and its purpose is to provide a liquid crystal display with excellent display performance without reducing the transparency of the transparent plastic plate. The purpose of the present invention is to provide a polarizing plate that can be used in various ways. Another object of the present invention is to provide a polarizing plate from which a lightweight and strong liquid crystal display can be obtained.

(Means for Solving the Problems) The present invention aims to eliminate the gap between the polarizing film and the protective plate of a liquid crystal display (using saturated copolymer polyester instead of polyvinyl butyral, which was conventionally used). By doing so, even if a transparent plastic plate is used as a protective plate, there is no risk that the transparency of the transparent plastic plate will decrease.

Therefore, a liquid crystal display with excellent dual display performance can be obtained.

It was completed based on the inventor's knowledge.

In the polarizing plate of the present invention, a saturated copolymerized polyester film is provided on one surface of a polarizing film, thereby achieving the above object.

The saturated copolymerized polyester used in the present invention is a linear saturated copolymerized polyester consisting of at least one type of polycarboxylic acid and at least one type of polyhydric alcohol. As a polyhydric carboxylic acid.

Examples include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sepathic acid, and dodecanedicarboxylic acid. Examples of polyhydric alcohols include glycols such as ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,4-butanediol, and triethylene glycol. By appropriately selecting one unit of these monomers and randomly copolymerizing them by a conventional method, the thermal properties and physical and mechanical properties of the polyester resin can be adjusted as desired. For the saturated copolymerized polyester, a resin having a softening point (ring and ball method, JISK-2531) of 140°C or lower, preferably 120°C or lower is used. When the softening point exceeds 140°C.

When integrating a polarizing film and a transparent plastic plate, it is necessary to raise the temperature to a high temperature.

Polarizing film deteriorates due to heat. Adhesion between the saturated copolymerized polyester film and the polarizing film and transparent plastic plate is also difficult to obtain. The outer surface of this saturated copolymerized polyester film (the surface not in contact with the polarizing film) has many irregularities formed on one side to ensure sufficient degassing when laminated onto a transparent plastic plate. is preferred.

The unevenness may be provided on both sides of the film, but in that case, the dimensional accuracy of the liquid crystal display decreases. It is preferable that the average spacing between adjacent recesses or adjacent protrusions be approximately twice or more than the 10-point average roughness in order to improve deaeration performance, and approximately 10 times or less is preferable. This is preferable in that the adhesiveness can be reduced when a highly adhesive resin is used. The average interval of the unevenness is usually 100 to 500 μm, preferably 200 to 300 μm. The 10-point average roughness is usually 20-100. +1m.

Preferably it is 25 to 70 μm. If the thickness is less than 25 μm, when a transparent plastic plate is laminated on a polarizing film, the sealing at the periphery will occur first, resulting in insufficient deaeration at the center. Therefore, the transparent plastic plate becomes opaque. Since there is a large amount of residual air even with a diameter of 70 μm or more, foaming occurs during heat and moisture resistance tests. Here, the 10-point average roughness means Rz measured in accordance with 15O-R468.

Methods for forming irregularities on a saturated copolymerized polyester film include, for example, an embossing roll method, a calendar roll method, a profile extrusion method, a mechanical etching method, and a method using male and female press plates.

Particularly preferred is the embossing roll method. The embossing roll method is a method in which an embossing roll on which unevenness corresponding to the unevenness to be imparted to the surface of a saturated copolymerized polyester film is formed is used as a forming press roll during resin film production.

The saturated copolymerized polyester film contains UV absorbers,
Antioxidants, colorants, adhesion modifiers such as metal salts of carboxylic acids, etc. may also be contained.

In particular, when an ultraviolet absorber is blended, harmful ultraviolet rays are blocked for polarizing films and liquid crystals, thereby improving weather resistance.

The polarizing film is not particularly limited, and any conventionally known film can be used. This is applied to one or both sides of a polarizing film that has been given polarizing properties.

Cellulose-based films such as cellulose triacetate.

It is obtained by laminating protective films such as polycarbonate films and polyethersulfone films. The polarizing film is, for example, a film of polyvinyl alcohol-based resin such as polyvinyl alcohol, polyvinyl formal, polyvinyl acecool, or saponified product of ethylene-vinyl acetate copolymer.

It is produced by impregnating it with a polarizing element such as iodine or dichroic dye and stretching it.

To manufacture the polarizing plate of the present invention 1. For example, the mirror side of a saturated copolymerized polyester film, which has a mirror surface on the negative side and an uneven surface on the other side, is applied to a polarizing film and heated (e.g.
It is preferable to apply pressure (for example, 0.5 to 5 kg/co) at a temperature of around 0°C.

In the polarizing plate of the present invention, a pressure-sensitive adhesive layer is preferably provided on the opposite side of the polarizing film from the saturated copolymerized polyester film. For this pressure-sensitive adhesive layer, for example, an acrylic resin such as acrylic acid (2-ethylhexyl)-methacrylic acid copolymer is used. By making the outer surface of the pressure-sensitive adhesive layer smooth, distortion of the liquid crystal cell is reduced. Furthermore, in the lamination of the pressure-sensitive adhesive layer and the liquid crystal cell, sufficient deaeration can be achieved even if the outer surface of the pressure-sensitive adhesive layer is smooth.

Such a polarizing plate is used, for example, in a liquid crystal display using a transparent plastic plate as a protective plate. Examples of transparent plastic plates include acrylic plates and polycarbonate plates.

Using this polarizing plate, a liquid crystal display is formed in a 7th, for example, 9th order manner.

Two polarizing films each having a saturated copolymerized polyester film on one side are laminated on the liquid crystal cell using, for example, a pressure-sensitive adhesive. A temporary transparent plastic is placed on top of the polyester film on this polarizing film. This structure is placed in an airtight body such as a rubber bag, and degassed under reduced pressure to a size of 650 mm and 11 g at a temperature of 50° C. or lower, preferably 30° C. or lower. The degassing time is preferably 5 minutes or more. Next, the rubber bag containing the structure is placed in a heating furnace such as a gear oven and heated to 560-140°C, preferably 65-85°C.
Heat to C. It is preferable to continue degassing during heating.

The rubber bag is taken out of the heating furnace, and after cooling to below 50°C, the construction is taken out. This construct is generally heated to 60 kg/cJ or more in an autoclave at a pressure of 3 kg/cJ or more.
Heated to ~140°C, preferably 65-85°C.

In this case, the structure may be pressurized and heated without being removed from the rubber bag. In this way, a transparent plastic plate is further laminated on the laminate of the liquid crystal cell and the polarizing film with the saturated copolymerized polyester film interposed therebetween.

On the surface of the saturated copolymerized polyester film laminated to the polarizing film and the pressure-sensitive adhesive layer.

A separator is provided if necessary. This separator has the function of maintaining the adhesiveness of the polyester film and the pressure-sensitive adhesive layer and preventing the adhesion of foreign matter. Examples of the separator include release films such as polyethylene films coated with silicone on one surface.

One example of a liquid crystal display using the polarizing plate of the present invention is as follows.

As shown in FIG. 1, an upper polarizing plate 1 is laminated on a liquid crystal cell 2, a transparent plastic plate 3 is provided on the upper polarizing plate 1, and a lower polarizing plate 1'' is placed below the liquid crystal cell 2. are laminated, and a reflective layer 4 made of aluminum foil or the like is further provided below.

The upper polarizing plate 1 consists of a saturated copolymerized polyester film 11 provided on one side of a polarizing film 10 and a pressure-sensitive adhesive layer 12 provided on the other side of the polarizing film 10.

The liquid crystal cell 2 has a liquid crystal cell glass 20.

It is composed of a liquid crystal 21 housed within a glass 20.

The pressure sensitive adhesive layer 12 is adhered to the liquid crystal cell glass 20, and the saturated copolymer polyester film 11 is adhered to the transparent plastic plate 3. Note that since the reflective layer 4 provided on the lower polarizing plate 1° is generally extremely thin, it is usually adhered to the polarizing film 10° by a pressure-sensitive adhesive layer 12° instead of the polyester film 11 of the upper polarizing plate 1. Film 10' is pressure sensitive adhesive layer 12
It is adhered to the liquid crystal cell 2 by .

(Example) The present invention will be described below with reference to examples.

Implementation ±1 Plate-shaped saturated copolymer polyester (softening point 105°C.

Byron 560. manufactured by Toyobo Co., Ltd.) at 70℃, 50 kg
Pressing was performed using male and female press plates under the conditions of /cJ.

As shown in Fig. 2, the - side is a mirror surface and the other side is uneven.
A saturated copolymerized polyester film 11 having a thickness of 380 μm was obtained. The unevenness was 40 μm in ISO/Rz.

This copolymerized polyester film 11 and cellulose triacetate/polyvinyl alcohol/cellulose triacetate/polyvinyl alcohol/
Cellulose triacetate three-layer polarizing film, J! 7sa
180 μm) 10 was heated and heated so that the mirror side of the polyester film was in contact with one of the cellulose triacetate layers.
Pressure was applied and the layers were laminated. On the other cellulose triacetate layer, an acrylic pressure-sensitive adhesive prepared separately by a conventional method was applied to form an adhesive layer 12, thereby obtaining a polarizing plate 1. For the acrylic pressure-sensitive adhesive layer, an acrylic acid (2-ethylhexyl)-methacrylic acid copolymer containing polyisocyanate (triepoxyprobyl isocyanate) as a crosslinking agent was used.

The obtained polarizing plate 1 was cut into a size of 100 mm x 250 mm, and the pressure-sensitive adhesive layer was directed to the glass plate 20 of the liquid crystal cell, and the pressure-sensitive adhesive layer was gradually adhered to the glass surface by pushing out air. Next, an acrylic plate 3 (Mitsubishi Acrylite, 1
00Ryu

The thus obtained construct was placed in a rubber bag and degassed under reduced pressure for 10 minutes at room temperature (20° C.) to 700 mmt1 g or less. Next, this rubber bag was heated in an open gear for 30 minutes to a surface temperature of 70°C while degassing (preliminary pressing). Furthermore, the rubber bag was placed in a pneumatic autoclave and heated to 70°C under a pressure of 5 kg/cut to adhere the saturated copolyester film to the acrylic plate (this press).The maximum temperature was maintained for 20 minutes. there were. The saturated copolymerized polyester film and the acrylic plate were sufficiently degassed, and no air bubbles remained in the resulting liquid crystal display.

The liquid crystal display thus obtained had excellent transparency, and no phenomena such as whitening of the acrylic plate were observed. Using this liquid crystal display as a sample, a moisture resistance test (6
A heat resistance test (80'C, 500 hours) was conducted. As a result, the polarizing plate did not peel off not only at the center of the sample but also at the periphery, and no abnormalities such as bubbles or wrinkles were observed.

A saturated copolymerized polyester film with a 10-point average roughness of 50 μm for unevenness provided on one side was used, and in place of the acrylic, a polycarbonate plate <2*m thick, 100 mm x 250 mm, and a kneepilon sheet was used. A liquid crystal display was obtained in the same manner as in Example 1, except that a liquid crystal display material (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used.

The obtained liquid crystal display had excellent transparency, and no phenomenon such as whitening of the polycarbonate plate was observed. When this liquid crystal display was subjected to a moisture resistance test and a heat resistance test in the same manner as in Example 1, no abnormalities such as peeling of the polarizing plate, bubbles, or wrinkles were observed.

Comparative polyvinyl butyral resin (average degree of polymerization 1700°, degree of butyralization 65 mol%, residual vinyl alcohol 34.5
A polyvinyl butyral & Jl composition was prepared by mixing 40 parts by weight of triethylene glycol-di-2-ethyl butyrate with 100 parts by weight (mol%).

After kneading this composition with a roll at 70°C.

Pressing was carried out using male and female press plates at 150° C. and 50 kg/cJ to obtain a plasticized polyvinyl butyral film having a thickness of 380 μm and having two mirror-finished surfaces and irregularities formed on the other surface. The unevenness had an average roughness of 35 μm at 1o point.

This plasticized polyvinyl butyral film was used in place of the saturated copolymerized polyester film.

A structure was formed by the same method as in Example 1.

This structure was subjected to preliminary pressing and main pressing in the same manner as in Example 1 to obtain a liquid crystal display. but.

The acrylic plate of the obtained liquid crystal display had turned white.

It lacked transparency.

A liquid crystal display was obtained in the same manner as in Comparative Example 1, except that the polycarbonate plate of Example 2 was used in place of the acrylic plate. However, the obtained liquid crystal display had a whitened polycarbonate plate and lacked transparency.

As is clear from the Examples and Comparative Examples, the polarizing plate of the present invention has a saturated copolymerized polyester film disposed between the polarizing film and the transparent plastic plate.
The transparent plastic plate will not whiten and lose its transparency. In conventional polarizing plates, the transparent plastic plate becomes white due to bleeding of the plasticizer in the plasticized polyvinyl butyral film placed between the polarizing film and the transparent plastic plate. Therefore, the transparency of the transparent plastic plate is reduced, and the display performance of the liquid crystal display is impaired.

(Effects of the Invention) The polarizing plate of the present invention is thus formed by integrating a polarizing film and a transparent plastic plate with a saturated copolymerized polyester film.

Unlike conventional transparent plastic plates, the transparent plastic plate does not whiten, and therefore there is no risk of its transparency decreasing. Therefore, a liquid crystal display with excellent dual display performance can be provided.

4. Figure 1 is a cross-sectional front view showing an embodiment of a liquid crystal display using the polarizing plate of the present invention, and Figure 2 is a cross-sectional front view showing an embodiment of the polarizing plate of the present invention. It is a cross-sectional front view.

1.1"...Polarizing plate, 2...Liquid crystal cell, 3...Transparent plastic plate, 4...Reflection layer, 10.10°.
... Polarizing film, 11... Saturated copolymerized polyester film.

12, 12'...Pressure sensitive adhesive layer, 20... Glass for liquid crystal cell.

21...Liquid crystal.

that's all

Claims (1)

[Claims] 1. A polarizing plate in which a saturated copolymerized polyester film is provided on one side of a polarizing film. 2. The softening point of the saturated copolymerized polyester film is 1.
The polarizing plate according to claim 1, which has a temperature of 40° C. or lower. 3. The polarizing plate according to claim 1, wherein a pressure-sensitive adhesive layer is provided on the surface of the polarizing film opposite to the saturated copolymerized polyester. 4. The polarizing plate according to claim 1, which is used in a liquid crystal display using a transparent plastic plate as a protection plate.